Field of Invention
The field of the present invention relates generally to ink jet apparatus, and more specifically to a method for operating an ink jet apparatus for providing selective control within a range of either the volume of the ink droplets ejected by the apparatus and/or the amount of ink striking a desired point on a recording medium.
The design of practical ink jet devices and apparatus for producing a single droplet of ink on demand is relatively new in the art. In prior drop on demand ink jet apparatus, the volume of each individual ink droplet is typically dependent upon the geometry of the ink jet apparatus, the type of ink used, and the magnitude of the pressure force developed within the ink chamber of the ink jet rejecting an ink droplet from an associated orifice. The effective diameter and design of the orifice, the volume and configuration of the ink chamber associated with the orifice, the transducer design, and the method of coupling the transducer to the ink chamber, are all factors determining the volume of individual ink droplets ejected from the orifice. Typically, once the mechanical design of an ink jet apparatus is frozen, control over the volume of the ejected ink droplets can only be obtained over a narrow range by varying the amplitude of the electrical pulses or dry voltage applied to the individual transducers of the ink jet apparatus or array.
The present inventor discovered that by operating the transducer of an ink jet in an iterative manner, for causing a plurality of successively higher, lower, or equal velocity ink droplets, or some combination thereof, to be ejected from the orifice of the ink jet, within a time period permitting the droplets to either merge in flight prior to striking a recording medium, or upon striking the recording medium at the same point, that broader control of the boldness and toning of printing could be obtained. The volume of ink striking a recording medium at a given point is thereby partly determined by the number of ink droplets merged prior to striking or at the point of striking.